1. Field of the Invention
The present invention relates to optical network systems, and in particular relates to a fiber sensing system.
2. Description of the Related Art
In recent years, Fiber Bragg Grating (FBG) has become an important element in the field of optical sensing. Among the sensing systems that use FBG primarily, the ability of providing diversified division multiplexing is one of the most important characteristics for the sensing systems. FBG can be applied to division multiplexing, such as wavelength-division multiplexing (WDM), space-division multiplexing (SDM), time-division multiplexing (TDM), code-division multiple access (CDMA), strength wavelength-division multiplexing and frequency-modulated continuous-wave (CW) multiplexing. Based on the existing division multiplexing technology and their ability to combine with each other, long range FBG sensing systems can be easily manufactured. Therefore, enhancing reliability and survivability of the FBG sensing system has become an important issue recently. In general, networks using architecture such as bus (in-line) topology, tree (star) topology and ring topology are unable to provide protection functions for the sensing system. For instance, when a fault point appears on a fiber line with bus topology, the fiber sensor is no longer able to provide any sensing for any part of the fiber line beyond the fault point. Therefore, there is a need for a fiber sensing system to completely sense all optical networks.